Sustained-release composition and process for producing the same

ABSTRACT

Present invention is to provide a sustained-release composition which contains a physiologically active substance in high content even when gelatin is not included, and suppresses its initial excessive release and, thus, can achieve a stable release rate over about one month. A sustained-release composition containing a lactic acid-glycolic acid polymer having a ratio or weight average molecular weight and number average molecular weight of about 1.90 or lower, or a salt thereof, and a physiologically active substance.

TECHNICAL FIELD

[0001] The present invention relates to a sustained-release preparationof a physiologically active substance and a process for producing thesame.

BACKGROUND ART

[0002] In JP-A 60-100516, a sustained-release microcapsule of awater-soluble drug, which comprises a particle of an average diameter of2 to 200 μm containing a water-soluble drug dispersed in a matrixcomprising a lactic acid-glycolic acid copolymer having weight averagemolecular weight of about 5000 to 200000 and comprising about 100 to 50%by weight of lactic acid and about 0 to 50% by weight of glycolic acid,and which is prepared by a method of drying in water is disclosed.

[0003] In JP-A 62-201816, a sustained-release microcapsule characterizedin that the viscosity of a W/O type emulsion upon preparation of a W/O/Wtype emulsion is adjusted to about 150 to 10000 cp, and a process forpreparing the same are disclosed.

[0004] In JP-A 62-54760, there are disclosed a biodegradablepolyoxycarboxylic ester which is a copolymer or a polymer having thecontent of water-soluble oxycarboxylic acid of less than 0.01 mole/100 gin terms of a monobasic acid and having a weight average molecularweight of about 2000 to 50000, and an injection sustained-releasemicrocapsule containing the polymer.

[0005] In JP-A 61-28521, there are disclosed a lactic acid-glycolic acidcopolymer which has weight average molecular weight of about 5000 to30000, does not contain a catalyst, has the dispersibility (by a gelpermeation chromatography method) of about 1.5 to 2 and comprises about50 to 95% by weight of lactic acid and 50 to 5% by weight of glycolicacid, and a pharmaceutical containing the polymer as a base.

[0006] In JP-A 6-192068, there is disclosed a process for preparing asustained-release microcapsule, which comprises heating a microcapsuleat a temperature higher than the glass transition temperature of apolymer, at which respective particles of the microcapsule do not adhereto each other.

[0007] In JP-A 4-218528, there is disclosed a method for purifyingbiodegradable aliphatic polyester, which comprises dissolving abiodegradable aliphatic polyester containing a low-molecular weightpolymer having a molecular weight of 1,000 or smaller in an organicsolvent, adding water thereto to precipitate a polymeric substance, andremoving low-molecular weight polymer having molecular weight of 1,000,and there is described that water is added at 50 to 150(ratio by volume)relative to 100 of the organic solvent.

OBJECTS OF THE INVENTION

[0008] The present invention is to provide a sustained-releasepreparation which does not contain gelatin and contains aphysiologically active substance in a large amount, and which canachieve a stable release rate over about one month by suppressing anyinitial excessive release of physiologically active substance.

SUMMARY OF THE INVENTION

[0009] In order to solve the aforementioned problem, the presentinventors studied intensively and, as a result, found asustained-release preparation which contains a physiologically activesubstance in a large amount without containing gelatin and which cansuppress any initial excessive release of physiologically activesubstance to achieve a stable release rate over about one month, bypreparing a polymer having a ratio of weight average molecular weight tonumber average molecular weight of PLGA as a base about 1.90 or lower,or by using a lactic acid-glycolic acid polymer having weight averagemolecular weight of about 11,600 to about 140,000 or a salt thereof,which resulted in completion of the present invention.

[0010] That is, the present invention provides:

[0011] (1) A sustained-release composition containing a lacticacid-glycolic acid polymer having a ratio of weight average molecularweight to number average molecular weight of about 1.90 or lower, or asalt thereof, and a physiologically active substance,

[0012] (2) the sustained-release composition described in the (1),wherein the physiologically active substance is a physiologically activepeptide,

[0013] (3) the sustained-release composition described in the (2),wherein the physiologically active substance is an LH-RH derivative,

[0014] (4) the sustained-release composition described in the (1),wherein weight average molecular weight of a lactic acid-glycolic acidpolymer is about 3,000 to about 100,000,

[0015] (5) the sustained-release composition described in the (4),wherein weight average molecular weight of a lactic acid-glycolic acidpolymer is about 8,000 to about 15,000,

[0016] (6) the sustained-release composition described in the (1),wherein the ratio of the low molecular weight fraction of molecularweight of lactic acid-glycolic acid polymer of about 3,000 or smaller isabout 9% or lower,

[0017] (7) the sustained-release composition described in the (6),wherein the ratio of the low molecular weight fraction of molecularweight of lactic acid-glycolic acid polymer of about 3,000 or smaller isabout 3% to about 9%,

[0018] (8) the sustained-release composition described in the (1),wherein said polymer has a molar ratio of lactic acid to glycolic acidof from 100:0 to 40:60,

[0019] (9) the sustained-release composition described in the (1),wherein said polymer has a molar ratio of lactic acid to glycolic acidof from 70:30 to 80:20,

[0020] (10) the sustained-release composition described in the (3),wherein the LH-RH derivative is a peptide represented by the formula:5-oxo-Pro-His-Trp-Ser-Tyr-Y-Leu-Arg-Pro-Z

[0021] wherein Y denotes DLeu, DAla, DTrp, DSer(tBu), D2Nal orDHis(ImBzl), and Z denotes HN-C₂H₅ or Gly-NH₂, or a salt thereof,

[0022] (11) the sustained-release composition described in the (3),wherein the LH-RH derivative is a peptide represented by the formula:5-oxo-Pro-His-Trp-Ser-Tyr-DLeu-Leu-Arg-Pro-NH— C₂H₅,

[0023] or acetate thereof,

[0024] (12) the sustained-release composition described in the (3),wherein the LH-RH derivative or a salt thereof is contained at about 5%(w/w) to about 24% (w/w) in the sustained-release composition,

[0025] (13) the sustained-release composition described in the (1),wherein the physiologically active substance or a salt thereof isslightly water-soluble or water-soluble,

[0026] (14) the sustained-release composition described in the (1),which is for injection,

[0027] (15) the sustained-release composition described in the (1),which releases a physiologically active substance or a salt thereof overat least two weeks,

[0028] (16) the sustained-release composition described in the (1),which does not contain a drug retaining substance,

[0029] (17) the sustained-release composition described in the (1),which does not contain gelatin,

[0030] (18) a process for producing the sustained-release composition asdefined in the (1), which comprises removing a solvent from a mixedsolution containing a physiologically active substance or a salt thereofand a lactic acid-glycolic acid polymer having a ratio of weight averagemolecular weight to number average molecular weight of about 1.90 orlower, or a salt thereof,

[0031] (19) the process described in the (18), which comprises mixingand dispersing a physiologically active substance or a salt thereof in asolution, in an organic solvent, containing a lactic acid-glycolic acidpolymer having a ratio of weight average molecular weight to numberaverage molecular weight of about 1.90 or lower, or a salt thereof, andremoving the organic solvent,

[0032] (20) the process described in the (19), wherein thephysiologically active substance or a salt thereof is used as an aqueoussolution containing the physiologically active substance or a saltthereof,

[0033] (21) a pharmaceutical comprising the sustained-releasecomposition as defined in the (1),

[0034] (22) an agent for preventing or treating prostate cancer,prostatomegaly, endometriosis, hysteromyoma, metrofibroma, precociouspuberty, dysmenorrhea and breast cancer, or a contraceptive, whichcomprises the sustained-release composition as defined in the (3),

[0035] (23) an agent for preventing recurrence of breast cancer afterthe operation for premenopausal breast cancer, which comprises thesustained-release composition as defined in the (3),

[0036] (24) a method for preventing or treating prostate cancer,prostatomegaly, endometriosis, hysteromyoma, metrofibroma, precociouspuberty and dysmenorrhea, or a contraceptive, which comprisesadministering to a mammal an effective dose of the sustained-releasecomposition as defined in the (3),

[0037] (25) a method for preventing recurrence of breast cancer afterthe operation for premenopausal breast cancer, which comprisesadministering to a mammal an effective dose of the sustained-releasecomposition as defined in the (3),

[0038] (26) a process for producing a lactic acid-glycolic acid polymerhaving a weight average molecular weight of about 8,000 to about 15,000and having a ratio of weight average molecular weight to number averagemolecular weight of about 1.90 or lower, or a salt thereof, whichcomprises adding water to an organic solvent containing a lacticacid-glycolic acid polymer having weight average molecular weight ofabout 5,000 to about 15,000 at a ratio of less than about 5 to 50 (ratioby volume) relative to 100 of the organic solvent,

[0039] (27) the process for producing a polymer described in the (26),wherein the organic solvent is hydrophilic,

[0040] (28) the process for producing a polymer described in the (27),wherein the hydrophilic organic solvent is acetone,

[0041] (29) the process for producing a polymer described in the (26),wherein the ratio of water relative to 100 of the organic solvent isabout 10 to about 45 (ratio by volume),

[0042] (30) the process for producing a polymer described in the (26),wherein the ratio of water relative to 100 of the organic solvent isabout 40 (ratio by volume),

[0043] (31) a lactic acid-glycolic acid polymer having weight averagemolecular weight of about 8,000 to about 15,000 and having a ratio ofweight average molecular weight to number average molecular weight ofabout 1.90 or lower, or a salt thereof,

[0044] (32) use of lactic acid-glycolic acid polymer or salt thereofdescribed in the (31) for producing the sustained-release compositionwhich does not include gelatin,

[0045] (33) a microsphere containing a lactic acid-glycolic acid polymerhaving weight average molecular weight of about 11,600 to about 14,000or a salt thereof, and a LH-RH derivative or a salt thereof, and notcontaining gelatin,

[0046] (34) the microsphere described in the (33), wherein the LH-RHderivative or a salt thereof is a peptide represented by the formula:5-oxo-Pro-His-Trp-Ser-Tyr-Y-Leu-Arg-Pro-Z

[0047] wherein Y denotes DLeu, DAla, DTrp, DSer(tBu), D2Nal orDHis(ImBzl), and Z denotes HH,C₂H₅ or Gly-NH₂, or a salt thereof,

[0048] (35) the microsphere described in the (33), wherein the LH-RHderivative or a salt thereof is a peptide represented by the formula:5-oxo-Pro-His-Trp-Ser-Tyr-DLeu-Leu-Arg-Pro-NH— C₂H₅,

[0049] or acetate thereof,

[0050] (36) the microsphere described in the (33), wherein the LH-RHderivative or a salt thereof is contained at about 5% (w/w) to about 24%(w/w),

[0051] (37) the microsphere described in the (33), which is amicrocapsule,

[0052] (38) the microsphere described in the (33), wherein the LH-RHderivative or a salt thereof is released during at least more than 2weeks,

[0053] (39) an agent for preventing or treating prostate cancer,prostatomegaly, endometriosis, hysteromyoma, metrofibroma, precociouspuberty and dysmenorrhea, or a contraceptive, which comprises themicrosphere described in the (33),

[0054] (40) an agent for preventing recurrence of breast cancer afterthe operation for premenopausal breast cancer, which comprises themicrosphere described in the (33),

[0055] (41) a method for preventing or treating prostate cancer,prostatomegaly, endometriosis, hysteromyoma, metrofibroma, precociouspuberty and dysmenorrhea, or a contraceptive, which comprisesadministering to a mammal an effective dose of the microsphere describedin the (33),

[0056] (42) a method for preventing recurrence of breast cancer afterthe operation for premenopausal breast cancer, which comprisesadministering to a mammal an effective dose of the microsphere describedin the (33).

DETAILED DESCRIPTION OF THE INVENTION

[0057] The physiologically active substance used in the presentinvention is not particularly limited as long as it is pharmaceuticallyuseful, and a non-peptide compound or peptide compound. Examples of asuitable non-peptide compound include an agonist, an antagonist, and acompound having the enzyme inhibiting activity. In addition, as thepeptide compound, for example, a physiologically active peptide ispreferable. Physiologically active peptides having a molecular weight ofabout 3000 to about 40,000, preferably about 4000 to about 30,000, morepreferably about 5000 to about 200,000 are suitable.

[0058] Examples of the physiologically active peptide includeluteinizing hormone-releasing hormone (LH-RH), insulin, somatostatin,somatotropin, growth hormone-releasing hormone (GH-RH), prolactin,erythropoietin, adrenal cortical hormone, melanocyte-stimulatinghormone, thyroid hormone-releasing hormone, thyroid-stimulating hormone,luteinizing hormone, follicle-stimulating hormone, vasopressin,oxytocin, calcitonin, gastrin, secretin, pancreozymin, cholecystokinin,angiotensin, human placental lactogen, human chorionic gonadotropin,enkephalin, endorphin, kyotrophin, tuftsin, thymopoietin, thymosin,thymotimurin, thymus humoran factor, blood thymus factor, tumor necrosisfactor, colony-inducing factor, motilin, dynorphin, bombesin,neurotensin, cerulein, bradykinin, atrial natriureticexcretion-increasing factor, nerve growth factor, cell growthstimulator, neurotrophic factor, peptides having the endothelinantagonistic activity and derivatives, fragments thereof and derivativesof the fragments.

[0059] The physiologically active substance used in the presentinvention may be itself or maybe a pharmacologically salt thereof.

[0060] When the physiologically active substance has a basic group suchas an amino group, examples of such salts include salts with inorganicacids (also referred to as inorganic free acid)(for example, carbonicacid, bicarbonic acid, hydrochloric acid, sulfuric acid, nitric acid,boric acid and the like), and organic acids (also referred to as organicfree acid)(for example, succinic acid, acetic acid, propionic acid,trifluoroacetic acid and the like), when the physiologically activesubstance has an acidic group such as a carboxyl group and the like,examples of such the salt include salts with inorganic base (alsoreferred to as inorganic free base)(for example, alkali metal such assodium, potassium and the like, alkaline earth metal such as calcium,magnesium and the like), and organic bases (also referred to as organicfree base)(for example, organic amines such as triethylamine and thelike, basic amino acids such as arginine and the like). In addition, thephysiologically active peptide may form a metal complex compound (forexample, copper complex, zinc complex and the like).

[0061] Preferable examples of the physiologically active peptide includeLH-RH derivatives or salts thereof which are effective for hormonedependent diseases, in particular, sex hormone dependent cancers (forexample, prostate cancer, uterine cancer, breast cancer, pituitary glandtumor and the like), sex hormone dependent disease such asprostatomegaly, endometriosis, hysteromyoma, precocious puberty,dysmenorrhea, amenorrhea, premenstrual syndrome, multilocular ovarysyndrome and the like, contraception (or, when the rebound activityafter cease of administration is utilized, infertility), prevention ofrecurrence of breast cancer after the operation for premenopausal breastcancer. Further, examples include LH-RH derivatives or salts thereofeffective for benign or malignant tumors which are sex hormoneindependent but LH-RH sensitive.

[0062] Specific examples of the LH-RH derivatives or salts thereofinclude peptides described in Treatment with GnRH analogs: Controversiesand perspectives (The parthenon Publishing Group Ltd.) published in1996, JP-A 3-503165, JP-A 3-101695, JP-A 7-97334 and JP-A 8-259460.

[0063] Examples of the LH-RH derivatives include LH-RH agonists andLH-RH antagonists. As the LH-RH antagonists, for example, aphysiologically active peptide represented by the general formula [I]:X-D2Nal-D4ClPhe-D3Pal-Ser-A-B-Leu-C-Pro-DAlaNH₂

[0064] [wherein X denotes N(4H₂-furoyl)Gly or NAc, A denotes a residueselected from NHeTyr, Tyr, Aph(Atz), and NMeAph(Atz), B denotes aresidue selected from DLys(Nic), DCit, DLis(AzaglyNic), DLis(AzaglyFur)DhArg(Et₂), DAph(Atz) and DhCi, and C denotes Lys(Nisp), Arg orhArg(Et₂)],

[0065] and a salt thereof are used.

[0066] As the LH-RH agonist, for example, a physiologically activepeptide represented by the general formula [II]:5-oxo-Pro-His-Trp-Ser-Tyr-Y-Leu-Arg-Pro-Z

[0067] [wherein Y denotes a residue selected from DLeu, DAla, DTrp,DSer(tBu), D2Nal and DHis(ImBzl), and Z denotes NH—C₂H₅ or Gly-NH₂]

[0068] or a salt thereof is used. In particular, a peptide wherein Y isDLeu and Z is NH—C₂H₅ (that is, Peptide A represented by5-oxo-Pro-His-Trp-Ser-Tyr-DLeu-Leu-Arg-Pro-NH—C₂H₅; Leuprorelin) or asalt thereof (for example, acetate) is suitable.

[0069] These peptides can be prepared by the methods described in theaforementioned publications or patent publications or similar methods.

[0070] Abbreviations used in the present specification have thefollowing meanings: Abbreviation Name N(4H₂-furoyl)Gly:N-tetrahydrofuroylglycine residue NAc N-acetyl group N2NalD-3-(2-naphthyl)alanine residue D4ClPhe D-3-(4-chloro)phenylalanineresidue D3Pal D-3-(3-pyridyl)alanine residue NMeTyr N-methyltyrosineresidue Aph(Atz) N-[5′-(3′-amino-1′H-1′,2′,4′- triazolyl)]phenylalanineresidue NMeAph(Atz) N-methyl-[5′-(3′-amino-1′H-1′,2′,4′-triazolyl)]phenylalanine residue DLys(Nic) D-(e-N-nicotinoyl)lysineresidue Dcit D-citrulline residue DLys(AzaglyNic)D-(azaglycylnicotinoyl)lysine residue DLys(AzaglyFur)D-(azaglycylfuranyl)lysine residue DhArg(Et₂)D-(N,N′-diethyl)homoarginine residue DAph(Atz)D-N-[5′-(3′-amino-1′H-1′,2′,4′- triazolyl)]phenylalanine residue DhCiD-homocitrulline residue Lys(Nisp) (e-N-isopropyl)lysine residuehArg(Et₂) (N,N′-diethyl)homoarginine residue

[0071] Regarding other acids, abbreviation is expressed based onabbreviations according to IUPAC-IUB Commission on BiochemicalNomenclature (European Journal of Biochemistry, Vol.138, pp9-37 (1984))or the conventional abbreviations in the art. In addition, when an aminoacid can have an optical isomer, it denotes L-amino acid unlessindicated otherwise.

[0072] As a lactic acid-glycolic acid polymer used in the presentinvention, a lactic acid-glycolic acid polymer having a ratio of weightaverage molecular weight of the lactic acid-glycolic acid polymer tonumber average molecular weight of the lactic acid-glycolic acid polymerof about 1.90 or lower is preferably used.

[0073] A lactic acid-glycolic acid copolymer may be a salt. Examples ofthe salt include salts with inorganic bases (for example, alkali metalsuch as sodium, potassium and the like, and alkaline earth metal such ascalcium, magnesium and the like) or organic bases (for example, organicamines such as triethylamine and the like, and basic amino acids such asarginine and the like), salts with transition metals (for example, zinc,iron, copper and the like), and complex salts.

[0074] A constitutional molar ratio of the lactic acid-glycolic acidpolymer is preferably about 100/0 to about 40/60, more preferably about70/30 to about 80/20.

[0075] A optical isomer ratio of lactic acid which is one of minimumrepeating units of the “lactic acid-glycolic acid polymer” is preferablyin a range of D-isomer/L-isomer (mole/mole %) of about 75/25 to about25/75. In particular, the D-isomer/L-isomer (mole/mole %) in a range ofabout 60/40 to about 30/70 is frequently used.

[0076] A weight average molecular weight of the “lactic acid-glycolicacid polymer” is usually about 3,000 to about 100,000, preferably about3,000 to about 50,000, particularly preferably about 8,000 to about15,000.

[0077] A ratio of a low molecular weight fraction, having molecularweight of about 3,000 or smaller, of the “lactic acid-glycolic acidpolymer” is preferably about 9% or lower, more preferably about 3% to 9%or lower.

[0078] In addition, a lactic acid-glycolic acid polymer in the presentinvention has a ratio of weight average molecular weight of the lacticacid-glycolic acid polymer to number average molecular weight of thelactic acid-glycolic acid polymer of about 1.90 or lower, preferablyabout 1.40 to about 1.90, more preferably about 1.45 to about 1.80.

[0079] Further, preferable examples include:

[0080] (1) a lactic acid-glycolic acid polymer having a weight averagemolecular weight of about 3,000 to 100,000 and having a ratio of weightaverage molecular weight of a lactic acid-glycolic acid polymer tonumber average molecular weight of a lactic acid-glycolic acid polymerof about 1.90 or lower,

[0081] (2) a lactic acid-glycolic acid polymer having a weight averagemolecular weight of about 3,000 to 50,000 and having a ratio of weightaverage molecular weight of a lactic acid-glycolic acid polymer tonumber average molecular weight of a lactic acid-glycolic acid polymerof about 1.90 or lower,

[0082] (3) a lactic acid-glycolic acid polymer having a weight averagemolecular weight of about 8,000 to 15,000 and having a ratio of weightaverage molecular weight of a lactic acid-glycolic acid polymer tonumber average molecular weight of a lactic acid-glycolic acid polymerof about 1.90 or lower,

[0083] (4) a sustained-release composition described in the (1) to (3),wherein a ratio of a low molecular weight fraction, having molecularweight of about 3,000 or smaller, of a lactic acid-glycolic acid polymeris about 9% or lower, and

[0084] (5) a sustained-release composition described in the (1) to (3),wherein a ratio of a low molecular weight fraction, having molecularweight of about 3,000 or smaller, of a lactic acid-glycolic acid polymeris about 3% to about 9%.

[0085] More preferable examples include:

[0086] (6) a lactic acid-glycolic acid polymer having weight averagemolecular weight of about 3,000 to 100,000 and having a ratio of weightaverage molecular weight of a lactic acid-glycolic acid polymer tonumber average molecular weight of a lactic acid-glycolic acid polymerof about 1.40 to about 1.90,

[0087] (7) a lactic acid-glycolic acid polymer having a weight averagemolecular weight of about 3,000 to 50,000 and having a ratio of weightaverage molecular weight of a lactic acid-glycolic acid polymer tonumber average molecular weight of a lactic acid-glycolic acid polymerof about 1.40 to about 1.90,

[0088] (8) a lactic acid-glycolic acid polymer having weight averagemolecular weight of about 8,000 to 15,000 and having a ratio of weightaverage molecular weight of a lactic acid-glycolic acid polymer tonumber average molecular weight of a lactic acid-glycolic acid polymerof about 1.40 to about 1.90,

[0089] (9) a sustained-release composition described in the (6) to (8),wherein a ratio of a low molecular weight fraction, having molecularweight of about 3,000 or smaller, of a lactic acid-glycolic acid polymeris about 9% or lower, and

[0090] (10) a sustained-release composition described in the (6) to (8),wherein a ratio of a low molecular weight fraction, having molecularweight of about 3,000 or smaller, of a lactic acid-glycolic acid polymeris about 3% to about 9%.

[0091] Most preferable examples include:

[0092] (11) a lactic acid-glycolic acid polymer having weight averagemolecular weight of about 3,000 to 100,000 and having a ratio of weightaverage molecular weight of a lactic acid-glycolic acid polymer tonumber average molecular weight of a lactic acid-glycolic acid polymerof about 1.45 to about 1.80,

[0093] (12) a lactic acid-glycolic acid polymer having weight averagemolecular weight of about 3,000 to 50,000 and having a ratio of weightaverage molecular weight of a lactic acid-glycolic acid polymer tonumber average molecular weight of a lactic acid-glycolic acid polymerof about 1.45 to about 1.80,

[0094] (13) a lactic acid-glycolic acid polymer having weight averagemolecular weight of about 3,000 to 15,000 and having a ratio of weightaverage molecular weight of a lactic acid-glycolic acid polymer tonumber average molecular weight of a lactic acid-glycolic acid polymerof about 1.45 to about 1.80,

[0095] (14) a sustained-release composition described in the (11) to(13), wherein a ratio of a low molecular weight fraction, havingmolecular weight of about 3,000 or smaller, of a lactic acid-glycolicacid polymer is about 9% or lower, and

[0096] (15) a sustained-release composition described in the (11) to(13), wherein a ratio of a low molecular weight fraction, havingmolecular weight of about 3,000 or smaller, of a lactic acid-glycolicacid polymer is about 3% to about 9%.

[0097] Furthermore, a lactic acid-glycolic acid polymer having weightaverage molecular weight of about 11,600 to about 14,000 or a saltthereof may be used.

[0098] Weight average molecular weight and number average molecularweight in the present specification refer to molecular weight in termsof polystyrene measured by gel permeation chromatography (GPC) using asa standard substance ten kinds of monodisperse polystyrene having (GPC1)weight average molecular weight of 397000, 189000, 98900, 37200, 17100,9490, 5870, 2500, 1050 and 495.

[0099] Further, the amount of a low molecular weight fraction of thepolymer having a molecular weight of about 3,000 or smaller denotes theamount of a fraction having a molecular weight of about 3,000 or smallerwithin a weight average molecular weight distribution pattern obtainedin the aforementioned GPC measurement. More specifically, the amount ofthe area under the curve of a part corresponding to a molecular weightof about 3,000 or smaller relative to the area under the curve of thecalculated weight average molecular weight distribution pattern iscalculated. Measurement is performed by using a series of high speed GPCapparatus (manufactured by Toso, HLC-8120GPC, a detection method is bydifferential refractive index), TSKguardcolum Super H-L(4.6 mmi.d.x35mm), TSKgel SuperH4000(6 mmi.d.x150 mm)x2, and TSKgel SuperH2000(6mmi,d,x150 mm) (All columns are manufactured by Toso) and THF as amobile phase at a flow rate of 0.6 ml/min.

[0100] When the reaction between a lactic acid-glycolic acid polymer anda physiologically active substance is an ionic interaction, the maininteraction is between the physiologically active substance and terminalcarboxylic acid of a lactic acid-glycolic acid polymer. When the lowmolecular weight fraction is contained in a large amount, aphysiologically active substance readily interacts with a lacticacid-glycolic acid polymer of a low molecular weight having highreactivity. In a sustained-release injection agent, a physiologicallyactive substance involved in leakage upon preparation and initialrelease is mainly a physiologically active substance interacted withthis lactic acid-glycolic acid polymer of a low molecular weightfraction. In order to increase the content of the physiologically activesubstance and suppress the amount of its initial release, it isnecessary that a ratio of this lactic acid-glycolic acid polymer of alow molecular weight fraction is reduced below a certain level, and theratio of weight average molecular weight to number average molecularweight is reduced below a certain level. For this reason, for example,in order to obtain a lactic acid-glycolic acid polymer for an onemonth-type sustained release preparation, a lactic acid-glycolic acidpolymer is preferable, such a lactic acid-glycolic acid is preferablethat the aforementioned weight average molecular weight is about 8,000to about 15,000, a ratio of weight average molecular weight to numberaverage molecular weight is about 1.90 or lower, preferably about 1.40to about 1.90, more preferably about 1.45 to about 1.80, and the amountof a low molecular weight fraction having a weight average molecularweight of 3,000 or smaller is about 9% or lower, preferably about 3% toabout 9%.

[0101] The “lactic acid-glycolic acid polymer” can be prepared bydehydration polycondensation without a catalyst from lactic acid andglycolic acid (JP-A 61-28521) or ring-opening polymerization fromlactide and a cyclic diester compound such as glycolide and the like(Encyclopedic Handbook of Biomaterials and Bioengineering Part A:Materials, Volume 2, Marcel Dekker, Inc, 1995).

[0102] A lactic acid-glycolic acid polymer obtained by dehydrationpolycondensation without a catalyst from lactic acid and glycolic acidgenerally has a large amount of low molecular weight fraction, and has aratio of weight average molecular weight to number average molecularweight of about 2 or higher. The weight average molecular weight of alactic acid-glycolic acid copolymer used in the present specification isabout 5,000 to about 15,000. The amount of the low molecular weightfraction having a molecular weight of about 3,000 or smaller can varydepending on weight average molecular weight and, when weight averagemolecular weight is about 10,000, the amount of low molecular weightfraction having molecular weight of about 3,000 or smaller is about 10%or higher.

[0103] The resulting lactic acid-glycolic acid polymer can be purifiedby using an organic solvent to obtain an end polymer.

[0104] Examples of an organic solvent used in the present inventioninclude preferably a hydrophilic or a readily water-soluble organicsolvent such as, for example, acetone, tetrahydrofuran, dioxane,dimethylformamide and dimethyl sulfoxide and, inter alia, acetone ispreferably used.

[0105] The amount of water and organic solvent used in the presentinvention to be added is not particularly limited. However, when theamount of water is too large, reduction of the low molecular weightfraction is insufficient and, thus, it is difficult to obtain an endpolymer. On the other hand, when the amount of water is too small, thepolymer becomes difficult to precipitate and, therefore, recovery isdeteriorated and only a polymer having a higher molecular weight thanthe desired molecular weight is recovered. Usually, the amount of waterrelative to 100 of an organic solvent is about 5 to 50, preferably about10 to about 45, more preferably about 24 to about 40, particularlypreferably about 40. For example, 10 g of a lactic acid-glycolic acidpolymer is dissolved in 100 mL of acetone which is an organic solvent,40 mL of purified water is gradually added thereto while stirring by asuitable method, to precipitate an end polymer, which can be dried by asuitable method. When an end polymer can not be obtained by a singledissolution and precipitation step, this procedure may be repeated.

[0106] In the sustained-release preparation of the present invention, abase is preferably a lactic acid-glycolic acid polymer having a ratio ofweight average molecular weight to number average molecular weight ofabout 1.90 or lower, or a salt thereof, or a lactic acid-glycolic acidpolymer having weight average molecular weight of about 11,600 to about14,000 or a salt thereof. A constitutional molar ratio of lactic acidand glycolic acid is preferably 100/0 to 40/60. A physiologically activesubstance is preferably a LH-RH derivative and particularly preferably aLH-RH derivative is the peptide represented by the formula:5-oxo-Pro-His-Trp-Ser-Tyr-DLeu-Leu-Arg-Pro-NH—C₂H₅

[0107] or acetate thereof. The content of a LH-RH derivative or a saltthereof is preferably about 5% (w/w) to about 24% (w/w). Further,preferable is such a sustained-release preparation that does not containgelatin and releases a physiologically active substance or a saltthereof over at least two weeks.

[0108] A Method of Preparing a Microcapsule

[0109] The thus obtained lactic acid-glycolic acid polymer can be usedas a base for preparing a sustained-release preparation. A method ofpreparing a sustained-release composition, for example, a microcapsulecontaining a physiologically active substance or a salt thereof, and alactic acid-glycolic acid polymer or a salt thereof of the presentinvention is exemplified.

[0110] (I) A Method of Drying in Water

[0111] (i) O/W Method

[0112] In the present method, first, a solution of a lacticacid-glycolic acid polymer or a salt thereof in an organic solvent isprepared. It is preferable that an organic solvent used for preparing asustained-release preparation of the present invention has a boilingpoint of 120° C. or lower.

[0113] As the organic solvent, for example, halogenated hydrocarbon (forexample, dichloromethane, chloroform, dichloroethane, trichloroethane,carbon tetrachloride and the like), ethers (for example, ethyl ether,isopropyl ether and the like), fatty acid ester (for example, ethylacetate, butyl acetate and the like), aromatic hydrocarbon (for example,benzene, toluene, xylene and the like), alcohols (for example, ethanol,methanol and the like), and acetonitrile are used, and a solvent of themixture of them is used. As an organic solvent for a lacticacid-glycolic acid polymer or a salt thereof, inter alia,dichloromethane is preferable.

[0114] The concentration of lactic acid-glycolic acid polymer insolution in an organic solvent can vary depending on the molecularweight of a lactic acid-glycolic acid polymer and the type of organicsolvent. For example, when dichloromethane is used as an organicsolvent, the concentration is selected generally from about 0.5 to about70% by weight, more preferably about 1 to about 60% by weight,particularly preferably about 2 to about 50% by weight.

[0115] A physiologically active substance or a salt thereof is added to,and dissolved or dispersed in the thus obtained solution of a lacticacid-glycolic acid polymer in an organic solvent. Then, the resultingsolution in an organic solvent containing a composition comprising aphysiologically active substance or a salt thereof and a lacticacid-glycolic acid polymer or a salt thereof is added to an aqueousphase to form an 0 (oily phase)/W (aqueous phase) emulsion, a solvent inan oily phase is volatilized or diffused in an aqueous phase to preparea microcapsule. Upon this, a volume of an aqueous phase is selectedgenerally from about 1 to about 10,000-fold, more preferably about 5 to50,000-fold, particularly preferably about 10 to 2,000-fold an oilyphase volume.

[0116] An emulsifier may be added to an aqueous phase besides theaforementioned components. Any emulsifier may be used as long as it cangenerally form a stable O/W emulsion. Specifically, for example, anionicsurfactants (sodium oleate, sodium stearate, sodium laurylsulfate andthe like), nonionic surfactants (polyoxyethylene sorbitan fatty acidesters (Tween 80, Tween 60, manufactured by Atlas Powder),polyoxyethylene castor oil derivative (HCO-60, HCO-50, manufactured byNikko Chemical), polyvinyl pyrrolidone, polyvinyl alcohol,carboxymethylcellulose, lecithin, gelatin and hyaluronic acid are used.These may be used alone or in combination of some of them. Theconcentration upon use is preferably in a range of about 0.0001 to 10%by weight, more preferably in a range of about 0.001 to 5% by weight.

[0117] An osmotic pressure regulating agent may be added to an aqueousphase besides the aforementioned components. Any osmotic pressureregulating agent may be used as long as it produces osmotic pressurewhen formulated into an aqueous solution.

[0118] Examples of the osmotic pressure regulating agent includepolyhydric alcohols, monohydric alcohols, monosaccharides,disaccharides, oligosaccharide and amino acids or derivatives thereof.

[0119] As the polyhydric alcohols, for example, trihydric alcohols suchas glycerin and the like, pentahydric alcohols such as arabitol,xylitol, adonitol and the like, and hexahydric alcohols such asmannitol, sorbitol, dulcitol and the like are used. Inter alia,hexahydric alcohols are preferable, in particular, mannitol is suitable.

[0120] Examples of the monohydric alcohols include methanol, ethanol andisopropyl alcohol and, inter alia, ethanol is preferable.

[0121] As the monosaccharides, for example, pentoses such as arabinose,xylose, ribose, 2-deoxyribose and the like, and hexoses such as glucose,fructose, galactose, mannose, sorbose, rhamnose, fucose and the like areused and, among them, hexoses are preferable.

[0122] As the oligosaccharides, for example, trisaccharides such asmaltotriose, raffinose and the like, and tetrasaccharides such asstachyose and the like are used and, among them, trisaccharides arepreferable.

[0123] As the derivatives of monosaccharides, disaccharides andoligosaccharide, for example, glucosamine, galactosamine, glucuronicacid and galacturonic acid are used.

[0124] As the amino acids, any L-amino acids can be used and examplesthereof include glycine, leucine and arginine. Among them, L-arginine ispreferable.

[0125] These osmotic regulating agents may be used alone or incombination.

[0126] These osmotic regulating agents are used at the concentrationsuch that osmotic pressure of an external aqueous phase is about{fraction (1/50)} to about 5-fold, preferably about {fraction (1/25)} toabout 3-fold osmotic pressure of a physiological saline solution. Whenmannitol is used as an osmotic pressure regulating agent, itsconcentration is preferably 0.5% to 1.5%.

[0127] As a method of removing organic solvent, the method known per seor a similar method is used. Examples of the method include a method ofevaporating an organic solvent at a normal pressure or by reducingpressure to reduced pressure gradually while stirring with a propellertype stirrer, a magnetic stirrer or an ultrasound generating apparatus,a method of evaporating an organic solvent while the vacuum degree isregulated using a rotary evaporator, and a method of gradually removingan organic solvent using a dialysis membrane.

[0128] The thus obtained microcapsule is centrifuged or filtered torecover a free physiologically active substance or a salt thereof, adrug retaining substance and an emulsifier which are attached to thesurface of a microcapsule, are washed with distilled water severaltimes, and dispersed again in distilled water, which is lyophilized.

[0129] Since a microcapsule of the present invention uses as a base alactic acid-glycolic acid polymer having a ratio of weight averagemolecular weight to number average molecular weight of 1.90 or lower, ora salt thereof, or a lactic acid-glycolic acid polymer having weightaverage molecular weight of about 11,600 to about 14,000 or a saltthereof, the microcapsule can contain a drug in high content and, thus,it is not necessary that the microcapsule contains a drug retainingsubstance such as gelatin and a thickening agent.

[0130] These polymers can be used preferably for manufacturing asustained-release composition which releases a drug over at least twoweeks.

[0131] During the preparation step, an aggregation-preventing agent maybe added in order to prevent aggregation of particles. As theaggregation-preventing agent, for example, a water solublepolysaccharide such as mannitol, lactose, glucose and starches (forexample, corn starch and the like), an amino acid such as glycine, and aprotein such as fibrin and collagen are used. Among them, mannitol issuitable.

[0132] After lyophilization, if necessary, water and an organic solventin the microcapsule may be removed by warming within conditions underwhich microcapsules are not fused. Preferably, warming is performed at atemperature around or slightly higher than an intermediate glasstransition temperature of a microcapsule obtained by a differentialscanning calorimeter under the conditions of a temperature increasingrate of 10 to 20° C. per min. More preferably, warming is performed at atemperature around the intermediate glass transition temperature of amicrocapsule or in the temperature range from the intermediate glasstransition temperature of a microcapsule to a temperature higher byabout 30° C. than the intermediate glass transition temperature thereof.Preferably, warming is performed in the range of a temperature fromaround the intermediate glass transition temperature of a microcapsuleto higher by 10° C. than the intermediate glass transition temperaturethereof, more preferably in the range of a temperature from around theintermediate glass transition temperature to higher by 5° C. than theintermediate glass transition temperature.

[0133] Warming time can vary depending on the amount of microcapsule andis generally about 12 hours to 168 hours, preferably about 24 hours to120 hours, particularly preferably about 48 hours to 96 hours after thetemperature of the microcapsule itself reaches a prescribed temperature.

[0134] The warming method is not particularly limited as long as theaggregation of microcapsules is uniformly warmed by the method.

[0135] As a method of warming and drying, for example, a method ofwarming and drying in a thermostatic chamber, a fluidizing chamber, amoving chamber or a kiln, and a method of warming and drying with amicrowave are used. Among them, a method of warming and drying in athermostatic chamber is preferable.

[0136] (ii) W/O/W Method

[0137] First, a solution of a lactic acid-glycolic acid polymer or asalt thereof in an organic solvent is prepared, and the thus obtainedorganic solvent solution is referred to as an oily phase. The method ofpreparation is the same as that described in section (I)(i) above. Theconcentration of lactic acid-glycolic acid polymer in an organic solventcan vary depending on the molecular weight of lactic acid-glycolic acidpolymer and type of organic solvent and, for example, whendichloromethane is used as an organic solvent, the concentration isselected from generally about 0.5 to about 70% by weight, morepreferably about 1 to about 60% by weight, particularly preferably about2 to about 50% by weight.

[0138] Next, a solution or a dispersion of a physiologically activesubstance or a salt thereof [the solvent is water or a mixture of waterand alcohols (for example, methanol, ethanol and the like)] is prepared.

[0139] The concentration of physiologically active substance or a saltthereof to be added is generally 0.001 mg/ml to 10 g/ml, more preferably0.1 mg/ml to 5 g/ml, more preferably 10 mg/ml to 3 g/ml.

[0140] When the above-described physiologically active substance has abasic group such as amino group, salts of physiologically activesubstance include a salt with inorganic acid (also referred to asinorganic free acid)(for example, carbonic acid, acid carbonate,hydrochloric acid, sulfuric acid, nitric acid, boric acid etc.), organicacid (also referred to as organic free acid)(for example, succinic acid,acetic acid, propionic acid, trifluoracetic acid etc.).

[0141] When a physiologically active substance has a acidic group suchas carboxyl group, salts of physiologically active substance include asalt with inorganic base (also referred to as inorganic free base)(forexample, alkali metals such as sodium, potassium, alkali earth metalssuch as calcium, magnesium, etc.), organic base (also referred to asorganic free base)(for example, organic amines such as triethylamine,basic amino acids such as arginine, etc.). Further, physiologicallyactive peptides may form a metal complex compound (for example, coppercomplex, zinc complex etc.). When a physiologically active substance isa LHRH derivative, acetic acid is particularly preferably added.

[0142] As a solubilizing agent and a stabilizing agent, known ones maybe used. In order to dissolve or disperse a physiologically activesubstance or an additive, heating, shaking and stirring may be performedto such an extent that the activity is not lost, and thus obtainedaqueous solution is referred to as an inner aqueous phase.

[0143] The thus obtained inner aqueous phase and oily phase areemulsified by known methods such as a homogenization and ultrasound toform a W/O emulsion.

[0144] The volume of oily phase to be mixed is about 1 to about1000-fold, preferably 2 to 100-fold, more preferably about 3 to 10-foldrelative to the volume of the inner aqueous phase.

[0145] The range of the viscosity of the resulting W/o emulsion isgenerally about 10 to 10,000 cp, preferably about 100 to 5,000 cp,particularly preferably about 500 to 2,000 cp at about 12 to 25° C.

[0146] Then the resulting W/O emulsion comprising a physiologicallyactive substance or a salt thereof and a lactic acid-glycolic acidpolymer or a salt thereof is added to an aqueous phase to form a W(inner aqueous phase)/O (oily phase)/W (external aqueous phase), asolvent in an oily phase is volatilized or diffused into an externalaqueous phase to prepare a microcapsule. Upon this, a volume of anexternal aqueous phase is selected from generally about 1-fold to about10,000-fold, more preferably about 5-fold to about 50,000-fold,particularly preferably about 10-fold to about 2,000-fold a volume of anoily phase.

[0147] An emulsifier and an osomotic pressure regulating agent which maybe added to the aqueous phase besides the aforementioned components, andthe methods of preparation thereafter are the same as those described insection (I)(i) above.

[0148] (II) Phase Separating Method

[0149] When a microcapsule is prepared by the present method, acoacervating agent is gradually added to an organic solvent solutioncontaining a physiologically active substance or a salt thereof and alactic acid-glycolic acid polymer or a salt thereof described in amethod of drying in water in the (I) while stirring, to precipitate andsolidify a microcapsule. The volume of the coacervating agent may befrom about 0.01 to 1,000-fold, preferably about 0.05 to 500-fold,particularly preferably about 0.1 to 200-fold of the volume of the oilyphase.

[0150] The coacervating agent is not particularly limited as long as itis a polymer series, mineral oil series or plant oil series compoundwhich is compatible with an organic solvent, and does not dissolve thecomplex of the physiologically active substance or a salt thereof andthe lactic acid-glycolic acid polymer of a salt thereof. Specifically,for example, silicone oil, sesame oil, soybean oil, corn oil, cottonseedoil, coconut oil, linseed oil, mineral oil, n-hexane or n-heptane may beused. These may be used by mixing 2 or more of them.

[0151] The thus obtained microcapsule is recovered, washed repeatedlywith heptane or the like to remove the coacervating agent from thecomposition comprising a physiologically active substance or a saltthereof and a lactic acid-glycolic acid polymer or a salt thereof, whichis then dried under reduced pressure. Alternatively, washing isperformed in the same manner as that described as a method of drying inwater in section (I)(i) above, which is lyophilized and further warmedand dried.

[0152] (III) Spraying Drying Method

[0153] When a microcapsule is prepared by the present method, an organicsolvent solution containing a physiologically active substance or a saltthereof and a lactic acid-glycolic acid polymer or a salt thereofdescribed in a method of drying in water in section (I) is sprayed in adrying chamber of a spray dryer using a nozzle, and an organic solventin finely-divided droplets is volatilized in an extremely short time toprepare a microcapsule. Examples of the nozzle include to fluid nozzletype, pressure nozzle type, rotation disc type. Thereafter, ifnecessary, the microcapsule may be washed, lyophilized and furtherwarmed and dried by the same method as that described in a method ofdrying in water in section (I).

[0154] As a dosage form other than the aforementioned microcapsule, anorganic solvent solution containing a physiologically active substanceor a salt thereof and a lactic acid-glycolic acid polymer or a saltthereof described in a method of drying in water in a method ofpreparing a microcapsule (I) is dried by evaporating an organic solventand water while the degree of vacuum is regulated using, for example, arotary evaporator, which may be ground with a jet mill to obtain a finepowder (also referred to as microparticle).

[0155] Further, the ground fine powder may be washed by the same methodas that described in a method of drying in water in a method ofpreparing a microcapsule (I), lyophilized and further warmed and dried.

[0156] The thus obtained microcapsule or fine powder can achieve releaseof a drug corresponding to a decreasing rate of a lactic acid-glycolicacid polymer used.

[0157] The sustained-release composition of the present invention may beany form such as a microsphere, a microcapsule or a fine powder(microparticle), and a microcapsule is suitable.

[0158] The sustained-release composition of the present invention may beused as it is or the composition as a raw material may be formulatedinto a variety of dosage forms, and may be administered as an injectableagent or an implantable agent for intravenous, subcutaneous andintra-organ administration, as a transmucosal agent, an oral agent (forexample, capsule (for example, hard capsule, soft capsule and thelike)), solid preparations such as a granule, a powder and the like, orliquid agent such as a syrup agent, an emulsion, a suspension and thelike for nasal, rectal or uterine administration.

[0159] For example, for formulating the sustained-release composition ofthe present invention into an injectable agent, it is formulated into anaqueous suspension together with a dispersant (for example, surfactantssuch as Tween 80, HCO-60 and the like, and polysaccharides such assodium hyaluronate, carboxymethylcellulose, sodium arginate and thelike), a preservative (for example, methylparaben and propylparaben), anisotonic (sodium chloride, mannitol, sorbitol, glucose and proline), orit is dispersed into an oily suspension together with a plant oil suchas sesame oil or corn oil to obtain a sustained-release injection agentwhich can be actually used.

[0160] The particle diameter of a sustained-release composition of thepresent invention may be, when used as a suspension injection agent, insuch a range that satisfies a dispersion degree and the needlepenetrating property. For example, an average particle diameter is arange of about 0.1 to 300 μm, preferably about 0.5 to 150 μm, morepreferably about 1 to 100 μm.

[0161] In order to formulate a sustained-release composition of thepresent invention into an aseptic preparation, methods include, but arenot limited to a method of performing all steps aseptically inpreparation, a method of sterilizing with gamma-ray, a method of addingan antiseptic and the like.

[0162] Since a sustained-release composition of the present invention oflow toxicity, it can be used as a safe medicine for a mammal (forexample, human being, cow, pig, dog, cat, mouse, rat, rabbit and thelike), the dose of sustained-release composition of the presentinvention can vary depending on the type and content of thephysiologically active substance, the dosage form, duration time ofrelease of physiologically active substance, target disease and subjectanimal and effective amount of a physiologically active substance. Asingle dosage of physiologically active substance can be preferablyselected appropriately from a range of about 0.01 mg to 10 mg/kg weight,more preferably about 0.05 mg to 5 mg/kg weight per adult, for example,when used in a sustained-release preparation for a six monthspreparation.

[0163] A single dose of a sustained-release composition can bepreferably selected appropriately from about 0.05 mg to 50 mg/kg weight,more preferably about 0.1 mg to 30 mg/kg weight per adult.

[0164] Administration time can be appropriately selected depending onthe type and content of a physiologically active substance as a basis,dosage form, duration time of release of a physiologically activesubstance, target disease and a subject animal, such as once every fewweeks, once per month, once every few months (for example, three months,four months, six months etc) and the like.

[0165] A sustained-release composition of the present invention can beused as an agent for preventing or treating a variety of diseasesdepending on the type of physiologically active substance containedtherein and, for example, when a physiologically active substance is anLH-RH derivative, it can be used for preventing or treating hormonedependent diseases, in particular, sex hormone dependent cancers (forexample, prostate cancer, uterine cancer, breast cancer, pituitary glandtumor and the like), sex hormone dependent diseases such asprostatomegaly, endometriosis, hysteromyoma, precocious puberty,dysmenorrhea, amenorrhea, premenstrual syndrome, multilocular ovarysyndrome and the like, as an agent for preventing recurrence of breastcancer after the operation for premenopausal breast cancer, as an agentfor preventing or treating Alzheimer's disease or autoimmune diseases,and as a contraceptive (or, an agent for preventing or treatinginfertility, when the rebound activity after cease of administration isutilized). Further, it can also be used as an agent for preventing ortreating benign or malignant tumors which are known to be sex hormoneindependent but sensitive to LH-RH.

[0166] Therefore, hormone dependent diseases, in particular, sex hormonedependent cancers (for example, prostate cancer, uterine cancer, breastcancer, pituitary gland tumor and the like), sex hormone dependentdiseases such as prostatomegaly, endometriosis, hysteromyoma, precociouspuberty, dysmenorrhea, amenorrhea, premenstrual syndrome, multilocularovary syndrome and the like can be prevented or treated; and pregnancycan be prevented by administering to a mammal an effective dose of thetreating or preventing agent according to this invention, and alsorecurrence of breast cancer after the operation for premenopausal breastcancer can be prevented thereby.

EXAMPLES

[0167] The present invention will be explained more specifically by wayof Examples, Comparative Examples and Experimental Examples but thepresent invention is not limited by them.

Example A1

[0168] 10 g of a lactic acid-glycolic acid copolymer, having a weightaverage molecular weight of 9700 and a number average molecular weightof 5030, synthesized by dehydration polycondensation of lactic acid andglycolic acid is dissolved in 100 mL of acetone, and 40 mL of purifiedwater is added dropwise while stirring, to precipitate a polymer. Thesolution other than the precipitated glutinous starch syrup-like polymeris removed by decantation, and the resulting polymer is dried undervacuum. The polymer after drying has a yield of 8.37 g, a weight averagemolecular weight of 10500, and a number average molecular weight of6700.

Example A2

[0169] 4.87 g of the polymer obtained in Example A1 is dissolved in 8.03g of dichloromethane into an oily phase. The oily phase is mixed into anaqueous phase in which 0.597 g of acetate of Peptide A is dissolved in0.6 mL of purified water, which is primarily-emulsified at 25000 rpmusing a Polytron to obtain a W/o emulsion. This W/O emulsion is added to1000 mL of an 0.1% aqueous polyvinyl alcohol solution at 15° C., whichis converted into a W/o/W emulsion at 7000 rpm using a homomixer. Themicrocapsule is solidified by desolvation with a propeller stirrer overthree hours, then microcapsules which have passed through a 200 meshsieve are recovered, and lyophilized after 0.48 g of mannitol has beenadded. After lyophilization, the yield of the resulting microcapsule is3.92 g and the content of Peptide A is 10.18%.

Comparative Example A1

[0170] A microcapsule obtained using a lactic acid-glycolic acidcopolymer of Example A1 according to the same manner as that of ExampleA2 has a yield of 3.97 g, and a content of Peptide A of 9.50%.

Experimental Example A1

[0171] Microcapsules obtained in Example A2 and Comparative Example A1were dispersed in 0.3 ml of a dispersing medium (distilled water inwhich 0.25 mg of carboxymethylcellulose, 0.5 mg of Polysorbate 80 and 25mg of mannitol are dissolved) at an amount of 2.25 mg in terms ofPeptide A, which were administered to a male SD rat, 7 weeks old, in theback subcutaneously with a 22G injection needle, respectively. Aprescribed time after administration, rats were slaughtered,microcapsules remaining in the administration site was removed, andPeptide A remaining in it was quantitated, which was divided by eachinitial content to obtain a remaining rate as shown in Table 1. Further,Mw/Mn of polymers used in Example A2 and Comparative Example A1 aredescribed in Table. TABLE 1 Comparative Example A1 Example A2 Mw/Mn 1.931.57 1 day 84.64% 91.17% 2 week  32.2% 54.31% 4 week  2.54% 10.28%

[0172] It is apparent from Table 1, that when a polymer used in ExampleA2 and having Mw/Mn of 1.90 or lower rendered by acetone treatment isused to prepare a microcapsule, the initial release amount of Peptide Afrom the microcapsule is suppressed, and sustained release over a longterm of four weeks is ensured.

Example A3

[0173] 185.7 g of a lactic acid-glycolic acid copolymer having a weightaverage molecular weight of 10600 and a number average molecular weightof 6600 was dissolved in 300.1 g of dichloromethane, and the temperaturewas adjusted to 29.5° C. 330.2 g was weighed from this organic solventsolution, then mixed with an aqueous solution which had been obtained bydissolving 15.62 g of acetate of Peptide A in 15.31 g of distilled waterwhich had been warmed to 54.3° C., and stirred for 1 minute to obtain acrude emulsion, which was next emulsified under the conditions of 10,000rpm for two minutes using a homogenizer to form a W/O emulsion. Then,this W/O emulsion was cooled to 17.8° C., poured into 25 liters of a0.1% (w/w) aqueous polyvinyl alcohol (EG-40, manufactured byNihongoseikagaku) solution which had been adjusted to 17.9° C. inadvance, for 1 minute and 16 seconds, and stirred at 7,005 rpm usingHOMOMIC LINE FLOW (manufactured by Tokushukika) to obtain a W/O/Wemulsion. This W/O/W emulsion was stirred for 3 hours to volatilizedichloromethane or diffuse dichloromethane into an external aqueousphase, an oily phase was solidified, filtered through a sieve having 75μm opening, and a microcapsule was settled continuously at 2,000 rmpusing a centrifuge (H-600S, manufactured by Kokusanenshinki) andcollected. The collected microcapsule was dispersed again in a smallamount of distilled water, filtered through a sieve having 90 μmopening, which was dissolved by addition of 17.2 g of mannitol andlyophilized to obtain a powder. The microcapsule had a recovery rate of76.4% and a content of Peptide A in the microcapsule of 8.79%.

Experimental Example A2

[0174] About 26 mg of a microcapsule described in Example A3 wasdispersed in 0.3 ml of a dispersing medium (distilled water in which0.15 mg of carboxymethylcellulose, 0.3 mg of Polysorbate 80 and 15 mg ofmannitol are dissolved), which was administered to a male SD rat, 7weeks old, in the back subcutaneously with a 22G injection needle. Aprescribed time after administration, the rat was slaughtered,microcapsule remaining in the administration site was removed, Peptide Ain it was quantitated, which was divided by each initial content toobtain a remaining rate as shown in Table 2. TABLE 2 Time 1 day 1 week 1week 1 week 1 week 1 week Remaining 90.29% 68.06% 36.63% 12.75% 4.48%1.12% rate

[0175] As apparent from Table 2, even when preparation was scaled up,although the microcapsule described in Example A3 contains aphysiologically active substance at a high content, the remaining rateof a physiologically active substance one day after administration is asremarkably high as 90%. Therefore, when an Mw/Mn ratio of a polymer is alow value as about 1.6, the effect of considerably suppressing initialexcessive release of a physiologically active substance is exerted. Inaddition, this microcapsule achieves release of the physiologicallyactive substance at a constant rate over a long period of time.

Example B1

[0176] 197.7 g of a lactic acid-glycolic acid copolymer having a weightaverage molecular weight of 12600 and a number average molecular weightof 6400 was dissolved in 320.1 g of dichloromethane, press-filteredusing a 0.2 μm filter (EMFLOW, DFA4201FRP), and the temperature wasadjusted to about 30.0° C. 330.1 g was weighed, mixed with an aqueoussolution which had been obtained by dissolving 15.68 g of acetate ofPeptide A in 15.31 g of distilled water and had been warmed to 56.0° C.,stirred for 1 minute to obtain a crude emulsion, which was thenemulsified under the condition of 10,000 rpm for two minutes to obtain aW/O emulsion. Then, this W/O emulsion was cooled to 18.2° C., pouredinto 25 liters of a 0.1% (w/w) polyvinyl alcohol (EG-40, manufactured byNihongoseikagaku) which had been adjusted to 18.4° C. in advance, for 1minute and 46 seconds, stirred at 7,007 rpm using HOMOMIC LINE FLOW(manufactured by Tokushukika) to obtain a W/O/W emulsion. This W/O/Wemulsion was stirred for 3 hours to volatilize dichloromethane ordiffuse it into an external aqueous phase, then the oily phase wassolidified, filtered using a seive having 75 μm opening, andmicrocapsule was continuously settled at 2,000 rpm using a centrifuge(H-600S, manufactured by Kokusanenshinki) and collected. The collectedmicrocapsule was dispersed again in a small amount of distilled water,filtered using a seive having 90 μm opening, then dissolved by additionof 17.2 g of mannitol and lyophilized to obtain a powder. Themicrocapsule had a recovery rate of 73.47% and a content of Peptide A ina microcapsule of 8.43%.

Experimental Example B1

[0177] About 26.7 mg of the microcapsule described in Example B1 wasdispersed in 0.3 mg of dispersing medium (distilled water in which 0.15mg of carboxymethylcellulose, 0.3 mg of Polysorbate 80, and 15 mg ofmannitol were dissolved), and administered to a male SD rat, 7 weeksold, in the back subcutaneously with a 22G injection needle. Aprescribed time after administration, the rat was slaughtered, andmicrocapsule remaining at the administration site, and Peptide A in itwas quantitated, which was divided by each initial content to obtain aremaining rate as shown in Table 3. TABLE 3 Time 1 day 1 week 1 week 1week 1 week 1 week Remaining 82.43% 68.33% 47.07% 23.58% 9.05% 2.08%rate

[0178] As apparent from Table 3, microcapsule described in Example B1could contain a physiologically active substance at a high content evenwhen gelatin was not included, and remarkably suppressed initial releaseof a physiologically active substance and, this microcapsule released aphysiologically active substance over a long period of time.

Experimental Example B2

[0179] About 44.6 mg of a microcapsule described in Example B1 wasdispersed in 11.0 ml of a dispersing medium (distilled water in which0.15 mg of carboxymethylcellulose, 0.3 mg of Polysorbate 80, and 15 mgof mannitol were dissolved), which was administered to a beagle,weighing 7 to 12 kg, in the back subcutaneously with a 23G injectionneedle. A prescribed time after administration, blood was taken from aforefoot vein, the concentrations of Peptide A and testosterone werequantitated, and the results are shown in Table 4. TABLE 4 Time 1 day 1week 2 week 3 week 4 week 5 week Peptide A 2.21 0.398 0.525 0.433 0.6030.358 Testosterone 2.79 0.57 0.35 0.35 0.30 0.39

[0180] As apparent from Table 4, a microcapsule described in Example B1releases a physiologically active substance for a long period of time,and maintained the blood concentration of the physiologically activesubstance. In addition, the activity of the physiologically activesubstance released into blood was not lost and drug efficacy wasretained.

INDUSTRIAL APPLICABILITY

[0181] A sustained-release preparation of the present invention, havinga ratio of weight average molecular weight to number average molecularweight of PLGA as a base of about 1.90 or lower, or using a lacticacid-glycolic acid polymer having weight average molecular weight ofabout 11,600 to about 14,000 or a salt thereof as a base, contains aphysiologically active substance in high content even when gelatin isnot included, and suppresses initial excessive release ofphysiologically active substance and, thus, can achieve a stable releaserate over about one month.

[0182] That is, the preparation according to this invention has suchuseful effects that the manufacturing process and cost can be reducedbecause there is no need for using a drug retaining substance such asgelatin and a thickening agent, resulting reduced additives, and thatthe preparation can contain a drug at a high concentration without usinga drug retaining substance and a thickening agent; a sustained-releasecomposition which releases a drug over at least two weeks can beproduced; and the preparation having high stability can be producedowing to the increase of glass transition temperature.

1. A sustained-release composition containing a lactic acid-glycolicacid polymer having a ratio of weight average molecular weight to numberaverage molecular weight of about 1.90 or lower, or a salt thereof, anda physiologically active substance.
 2. The sustained-release compositionaccording to claim 1, wherein the physiologically active substance is aphysiologically active peptide.
 3. The sustained-release compositionaccording to claim 2, wherein the physiologically active substance is anLH-RH derivative.
 4. The sustained-release composition according toclaim 1, wherein weight average molecular weight of said lacticacid-glycolic acid polymer is about 3,000 to about 100,000.
 5. Thesustained-release composition according to claim 4, wherein weightaverage molecular weight of lactic acid-glycolic acid polymer is about8,000 to about 15,000.
 6. The sustained-release composition according toclaim 1, wherein the ratio of the low molecular weight fraction ofmolecular weight of lactic acid-glycolic acid polymer of about 3,000 orsmaller is about 9% or lower.
 7. The sustained-release compositionaccording to claim 6, wherein the ratio of the low molecular weightfraction of molecular weight of lactic acid-glycolic acid polymer ofabout 3,000 or smaller is about 3% to about 9%.
 8. The sustained-releasecomposition according to claim 1, wherein said polymer has a molar ratioof lactic acid to glycolic acid of from 100:0 to 40:60.
 9. Thesustained-release composition according to claim 1, wherein said polymerhas a molar ratio of lactic acid to glycolic acid of from 70:30 to80:20.
 10. The sustained-release composition according to claim 3,wherein the LH-RH derivative is a peptide represented by the formula:5-oxo-Pro-His-Trp-Ser-Tyr-Y-Leu-Arg-Pro-Z wherein Y denotes DLeu, DAla,DTrp, DSer(tBu), D2Nal or DHis(ImBzl), and Z denotes HN—, C₂H₅ orGly-NH₂, or a salt thereof.
 11. The sustained-release compositionaccording to claim 3, wherein the LH-RH derivative is a peptiderepresented by the formula:5-oxo-Pro-His-Trp-Ser-Tyr-DLeu-Leu-Arg-Pro-NH—C₂H₅, or acetate thereof.12. The sustained-release composition according to claim 3, wherein theLH-RH derivative or a salt thereof is contained at about 5% (w/w) toabout 24% (w/w) in the sustained-release composition.
 13. Thesustained-release composition according to claim 1, wherein thephysiologically active substance or a salt thereof is slightlywater-soluble or water-soluble.
 14. The sustained-release compositionaccording to claim 1, which is for injection.
 15. The sustained-releasecomposition according to claim 1, which releases a physiologicallyactive substance or a salt thereof over at least two weeks.
 16. Thesustained-release composition according to claim 1, which does notcontain a drug retaining substance.
 17. The sustained-releasecomposition according to claim 1, which does not contain gelatin.
 18. Aprocess for producing the sustained-release composition according toclaim 1, which comprises removing a solvent from a mixed solutioncontaining a physiologically active substance or a salt thereof and alactic acid-glycolic acid polymer having a ratio of weight averagemolecular weight to number average molecular weight of about 1.90 orlower, or a salt thereof.
 19. The process according to claim 18, whichcomprises mixing and dispersing a physiologically active substance or asalt thereof in an organic solvent solution containing a lacticacid-glycolic acid polymer having a ratio of weight average molecularweight to number average molecular weight of about 1.90 or lower or asalt thereof, and removing the organic solvent.
 20. The processaccording to claim 19, wherein the physiologically active substance or asalt thereof is used as an aqueous solution containing thephysiologically active substance or a salt thereof.
 21. A pharmaceuticalcomprising the sustained-release composition according to claim
 1. 22.An agent for preventing or treating prostate cancer, prostatomegaly,endometriosis, hysteromyoma, metrofibroma, precocious puberty, anddysmenorrhea, or a contraceptive, which comprises the sustained-releasecomposition according to claim
 3. 23. An agent for preventing recurrenceof breast cancer after the operation for premenopausal breast cancer,which comprises the sustained-release composition according to claim 3.24. A method for preventing or treating prostate cancer, prostatomegaly,endometriosis, hysteromyoma, metrofibroma, precocious puberty anddysmenorrhea, or a contraceptive, which comprises administering to amammal an effective dose of the sustained-release composition accordingto claim
 3. 25. A method for preventing recurrence of breast cancerafter the operation for premenopausal breast cancer, which comprisesadministering to a mammal an effective dose of the sustained-releasecomposition according to claim
 3. 26. A process for producing a lacticacid-glycolic acid polymer having weight average molecular weight ofabout 8,000 to about 15,000 and having a ratio of weight averagemolecular weight to number average molecular weight of about 1.90 orlower, or a salt thereof, which comprises adding water to an organicsolvent containing a lactic acid-glycolic acid polymer having weightaverage molecular weight of about 5,000 to 15,000 at a ratio of lessthan about 5 to 50 (ratio by volume) relative to 100 of the organicsolvent.
 27. The process for producing a polymer according to claim 26,wherein the organic solvent is hydrophilic.
 28. The process forproducing a polymer according to claim 27, wherein the hydrophilicorganic solvent is acetone.
 29. The process for producing a polymeraccording to claim 26, wherein the ratio of water relative to 100 of theorganic solvent is about 10 to about 45 (ratio by volume).
 30. Theprocess for producing a polymer according to claim 26, wherein the ratioof water relative to 100 of the organic solvent is about 40 (ratio byvolume).
 31. A lactic acid-glycolic acid polymer having weight averagemolecular weight of about 8,000 to about 15,000 and having a ratio ofweight average molecular weight to number average molecular weight ofabout 1.90 or lower, or a salt thereof.
 32. Use of lactic acid-glycolicacid polymer or salt thereof according to claim 31 for producing thesustained-release composition which does not include gelatin.
 33. Amicrosphere containing a lactic acid-glycolic acid polymer having weightaverage molecular weight of about 11,600 to about 14,000 or a saltthereof, and a LH-RH derivative or a salt thereof, and not containinggelatin.
 34. The microsphere according to claim 33, wherein the LH-RHderivative or a salt thereof is a peptide represented by the formula:5-oxo-Pro-His-Trp-Ser-Tyr-Y-Leu-Arg-Pro-Z wherein Y denotes DLeu, DAla,DTrp, DSer(tBu), D2Nal or DHis(ImBzl), and Z denotes HN—, C₂H₅ orGly-NH₂, or a salt thereof.
 35. The microsphere according to claim 33,wherein the LH-RH derivative or a salt thereof is a peptide representedby the formula: 5-oxo-Pro-His-Trp-Ser-Tyr-DLeu-Leu-Arg-Pro-NH—C₂H₅, oracetate thereof.
 36. The microsphere according to claim 33, wherein theLH-RH derivative or a salt thereof is contained at about 5% (w/w) toabout 24% (w/w).
 37. The microsphere according to claim 33, which is amicrocapsule.
 38. The microsphere according to claim 33, wherein theLH-RH derivative or a salt thereof is released during at least more than2 weeks.
 39. An agent for preventing or treating prostate cancer,prostatomegaly, endometriosis, hysteromyoma, metrofibroma, precociouspuberty and dysmenorrhea, or a contraceptive, which comprises themicrosphere according to claim
 33. 40. An agent for preventingrecurrence of breast cancer after the operation for premenopausal breastcancer, which comprises the microsphere according to claim
 33. 41. Amethod for preventing or treating prostate cancer, prostatomegaly,endometriosis, hysteromyoma, metrofibroma, precocious puberty anddysmenorrhea, or a contraceptive, which comprises administering to amammal an effective dose of the microsphere according to claim
 33. 42. Amethod for preventing recurrence of breast cancer after the operationfor premenopausal breast cancer, which comprises administering to amammal an effective dose of the microsphere according to claim 33.